1. Field of the Invention
The present invention relates to a navigation apparatus for a vehicle. More particularly, the present invention is directed to a voice output device of a voice navigation apparatus for improving the rate at which audible navigation instructions can be recognized by a driver while the driver is navigating a vehicle.
2. Discussion of Background Information
Conventional navigation apparatus have provided navigation instructions to a driver, when the driver is driving to a desired destination. Such navigation apparatus give instructions as to the correct route, so that the driver can properly navigate to a particular destination even though the driver is unfamiliar with the locality within which he or she is driving the vehicle. Several recent developments have been made of such navigation apparatus. Navigation apparatus have been provided which display a destination route, and which give instructions concerning the traveling direction to be taken at each spot, as necessary for navigation of the vehicle to the intended destination. The instructions are displayed on a display device such as a CRT display. The driver observes route information by viewing the display device as needed.
A disadvantage associated with such display-type navigation apparatus is that the driver must take his or her eyes away from the road in order to view the display in order to obtain routing information as needed. In order for the driver to confirm whether he or she is going in the right direction without being distracted from driving the vehicle, the driver must glance at the information on the display very quickly. However, a mere quick glance at the display may not be a satisfactory amount of time for the driver to sufficiently recognize and understand navigation instructions given by the navigation apparatus. Should the driver stop the vehicle in order to observe the display, the driver will delay the amount of time it takes to reach the intended destination. Repeated stops of the vehicle along the way will cause a large loss in time in reaching the destination.
In order to address the above-noted problems, voice navigation apparatus have provided voice navigation instructions, in addition to displayed navigation instructions, displayed on, e.g., a CRT display. More specifically, voice navigation apparatus have been provided with a loudspeaker for outputting voice instructions. The loudspeaker may be configured such that, for example, when it is determined that the vehicle should turn to the right at the next intersection, the loudspeaker will sound the words "turn to the right at the next intersection."
By the use of a voice navigation apparatus, the driver can audibly obtain route information without taking his or her eyes off the road in order to view a display. Thus, the driver can easily recognize navigation instructions audibly. However, when a driver has not completely recognized a voiced instruction sounded by a voice navigation apparatus, or when a driver forgets an instruction, the driver will not recognize the instruction's content and thus will be inconvenienced. In today's high-speed and complicated traffic situations, quick decisions are essential to proper and safe driving. If a driver fails to understand or fails to hear an audibly indicated routing instruction, the driver may miss an intersection, and thus may depart from the proper route to the intended destination. Thus, it is important in voice navigation apparatus that the driver can quickly recognize the content of the instructions with only one voiced instruction.